1. Field of the Invention
This invention relates to a resin composition, more particularly to a resin composition comprising a polysiloxane-grafted polyimide resin. This invention also relates to a flexible substrate formed from the resin composition.
2. Description of the Related Art
Recently, organic polymer materials have been widely used in various electronic components or devices so as to enhance various characteristics (for example, electrical insulation, heat resistance, mechanical property, etc.) of the electronic components or devices. Among them, polyimide polymer is most widely used in view of good mechanical and electrical properties. However, it is increasingly required to raise the properties and performances of the electronic components or devices in the art. Therefore, the mechanical properties (for example, flexibility, extensibility, etc.), the thermal properties (for example, low thermal expansion coefficient), insulation, or adhesion of polyimide polymer are required to be improved.
Conventionally, the physical properties, especially thermal or mechanical property, of polyimide polymer are modified by adding various reinforcing materials so as to enhance the applicability of polyimide polymer. Commonly used reinforcing materials include titanium dioxide, silicon dioxide, talc, etc. However, such a modification manner has problems in mixing homogeneity and compatibility. Furthermore, a flexible substrate formed therefrom may have a cloudy appearance.
JP2002-293933 discloses an alkoxy group-containing silane modified polyamic acid resin composition useful as an adhesive for a printed circuit board. The polyamic acid resin composition comprises an alkoxy group-containing silane modified polyamic acid resin and a solvent. The alkoxy group-containing silane modified polyamic acid resin is obtained by subjecting a polyamic acid and an epoxy group-containing alkoxysilane partial condensate to a reaction. The reaction is conducted between a carboxylic acid group of polyamic acid and an epoxy group of the alkoxysilane partial condensate so that the alkoxysilane partial condensate is bonded to a tetracarboxylic dianhydride moiety of the polyamic acid. However, when the alkoxy group-containing silane modified polyamic acid resin is further processed by heating, the alkoxy group-containing silane moiety on the polyamic acid resin would be dissociated therefrom. Therefore, the flexible substrate obtained after the subsequent processing may not have satisfactory mechanical and thermal properties, especially when being used for a flexible substrate for a flexible liquid crystal display or a flexible electronic book.
It is desirable in the art to provide a resin composition for forming a flexible substrate having satisfactory mechanical and thermal properties for an electronic device.